Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/144

106 106 S. V. WOOD, JUN., AND F. W. HARMER ON THE Trimley outliers, the only difference being that the Kirton protru- sion is partially capped with a patch of the Upper Glacial. Looking at the lines of section, as far as they are warranted by the actual exposures, it would appear as though the interglacial valleys thus excavated were, though much wider, shallower than the present ones ; but there are facts which point to the inference that in the same way that the valley of the Yare was deeper inter- glacially than it now is, so that of the Deben (and therefore, as an almost necessary sequence, the other valleys of South Suffolk) was somewhat deeper interglacially also. For instance, the Middle Glacial overlain by the Upper seems to plunge down so completely into the bottom of one of the principal lateral valleys which open out into that of the Deben, that, unless this were the case, the valley could have had no outlet. Section XXI. illustrates this, as well as the position of the important outlier of the Contorted Drift at Woodbridge and Hasketon, the much steeper character of the interglacial valley-slopes formed by it being proved by the great excavation in the Middle Glacial on the east, and by the well sunk through the Upper and Middle Glacial on the west side of it. In this section the sand overlain by the Upper Glacial Clay which fills the bottom of the rivulet- valley, is referred to the Middle Glacial (which is clearly recognizable where it underlies the Upper Glacial above the railway-cutting) ; but there is some uncertainty whether it be not the sand formed by the dissolution of the Crag ; but as it descends below the general level of the London-Clay floor of the Crag (which is well exposed in an adjoining valley where the Middle Glacial sweeps down below it in the way shown in this section), we have shown it as belonging to that formation. It is not improbable also that the bed 10, represented as valley- gravel, through which the Finn river and the Deben are represented as cutting, may be underlain by Middle Glacial gravel, or be that gravel postglacially reconstructed. The sinking of the well, shown in fig, 22, was watched and measured daily by one of us, and was interesting as furnishing a perfectly clear scarped section of this tableland down to the Crag- level, at a point but little more than half a mile from the numerous excavations in the Contorted Drift overlain by Upper Glacial, which occur at the Woodbridge and Hasketon brick-pits ; and it proved that this Drift, and any other formation, such as the Chillesford Clay, which may have existed between it and the Red Crag, had been completely removed before the deposition of the Middle Glacial. It also disclosed that the band of broken shells a few feet below the junction of the Middle with the Upper Glacial, which is so constant around Yarmouth, and from which were obtained the species given as from this formation in the Supplement to the ' Crag Mollusca/ was also present here ; and we obtained from it fragments of the fol- lowing species : — Tellina crassa, Gmel., Mya arenaria, Linn., Mactra arcuata?, Linn., Cyprina islandica, Sow., Cardium edide, Lin., Pec- tunculus glycymeris, Linn., Pecten opercularis, Linn. The particulars of the sinking were as follows : —